{
MICHAEL NICOLAI
> I need to extract the foreground color (black) and the background color
> (cyan) and insert them into vars for another procedure, that calls a
> picklist with Fg,Bg attributes. I can't change the way the procedure/
> function works, so I need to feed it =my= colors in =its= format.
>
Do you know the format of the attribute-byte? If not, here it is:
Bit 7 6 5 4 3 2 1 0
B b b b I f f f
B - 0 do not blink
1 character is blinking
bbb - backgroundcolor (3 Bit, giving you a total of 8 different values.)
I - 0 foregroundcolor is not intensified
1 foregroundcolor is intensified
fff - foregroundcolor (3 Bit + I, giving you a total of 16 different values.)
If you now want to extract the fore- or backgroundcolor you can easily do
that by performing an AND with either 70h, 0Fh or 07h.
The operator AND (if you don't know it):
AND a b | x a & b = x (or in Pascal: x := a and b;
---------
0 0 | 0
0 1 | 0
1 0 | 0
1 1 | 1
As you see, only when b is set to 1, the value in a is "getting through".
For example: a = 1011000111010111, b = 0001011011110110
then
1011000111010111
& 0001011011110110
--------------------
0001000011010110
When you look at it for a while you will see that, only where there is a 1
in the lower number, the value in the upper number is represented in the
result. Hence, you can use the AND operator to mask a portion of a number.
Now, let's get back to your colors: You mentioned 48 or NORM.
48 decimal equals to 00110000b. That is 'Not Blink', 'Color 3 for
Background', 'Color 0 for Foreground' and 'Foregroundcolor not intensified'.
What do you get, if you perform NORM & 70h? Let's see:
NORM 00110000
& 70h 01110000
---------------------
00110000 (= Backgroundcolor or Bg)
Not much you think, hm? Ok, but that has to do with the initial number NORM.
You will see "the light" as we proceed. :-)
Now, let us perform NORM & 0Fh:
NORM 00110000
& 0Fh 00001111
---------------------
00000000 (= Foregroundcolor WITH I)
and NORM & 07h:
NORM 00110000
& 07h 00000111
---------------------
00000000 (= Foregroundcolor WITHOUT I)
Hm, somewhat NORM was a bad choice as an example. But if you try it with
other values you will see how easy it is to "get a few bits out of a byte"!
}